Nowadays, electrical energy generating means, such as wind turbines, are fitted with copper or aluminium cables. However, due to the rising price of copper, fitting with aluminium cables is becoming increasingly popular. Particularly in the case of wind turbines which are between 50 m and 200 m high, large quantities of cable are required, so that the use of aluminium cables offers a considerable savings potential.
However, due to the great height of wind turbines, it is impossible to connect the generators arranged in the tower of the wind turbine by a single cable to the converter arranged in the base of the system. For this reason, cables are respectively preassembled in individual segments of the tower. To connect the cables of the individual segments, the cables have to be connected in an electrically conductive manner at the segment boundaries. As long as copper cables are used, crimping or screwing cables together is not a problem because material which adversely affects the electrical conductivity is not deposited on the copper surface, which material could lead to a reduction in the electrical conductivity of the connection during operation of the wind turbine.
However, this is different when aluminium cables are used. A crimp connection has to be protected against environmental influences. Furthermore, aluminium oxide must be prevented from forming at the connections since it significantly increases the transition resistance. In the case of cables which carry several 10 A or even several 100 A, an electrical transition resistance is always associated with a high power loss. Therefore, attempts must be made to configure the electrical transition resistance between the cables at the connection point such that it is as low as possible and, on the other hand, to provide a connection technology which can be assembled quickly.
Nowadays however, crimping the cables of the respective sections at the section boundaries is proposed. Here, a crimp sleeve is screwed onto the cables. To achieve this, the engineer has to climb into the tower, then cut the cables to length and strip them at the segment boundary. The engineer then has to coat the stripped ends of the cables with a conductive paste. This is to prevent aluminium oxide forming on the surfaces of the aluminium strands. Thereafter, the engineer has to push the crimp sleeve onto the free ends of the cables and screw it together with the cables using a lot of screws in a laborious process. The assembly described thus is time consuming and cost-intensive. Furthermore, the quality of the electrical connection is unstable, in other words over time, the electrical transition resistance increases because the conductive paste cannot fully prevent the formation of aluminium oxide.
In addition, a sufficiently effective strain relief has to be provided at the connection point. Enormous tensile forces arise at the connection point in the case of wiring harnesses of lengths of several tens of meters. Therefore, in addition to a good electrically conductive connection, a mechanically stable connection is also required. Nowadays, this is ensured by means of sturdy crimped connections and screwed connections of the cable cores.
For this reason, the object of the invention was to provide an electrical connection system which can be assembled in a particularly simple manner and which at the same time ensures a mechanical strain relief at the connection point.
This object is achieved in terms of the subject-matter by a connection system according to Claim 1.